Carbon Express Tank 25 400 spine Carbon Arrows - 12 Pack - The Tank 27 features 360 degree consistent spine and Diamond Weave construction. Straightness: 0.0025in. Weight Tolerance: 1 grain. All components sold seperately. Proprietary Diamond Weave - Unparalleled spine consistency .400" Spine - Ideal for average - short draw length and low poundage shooters. Versatile - Use as a 3D and Indoor arrow. BullDog Nock Collar - Unrelenting strength and durability for nock-end impacts (Free dozen with the purchase of shafts)